Child and teen BMI calculator

The path is pure arithmetic and table lookup with no network and no random seed, so coaching apps, school health tools, and prepaid API clients get identical JSON every time.

What child BMI measures and which inputs you need

Send weight as a positive finite number in kilograms; aliases weight_kg, body_weight, and mass_kg are accepted. Send height as centimeters; aliases height_cm, stature_cm, and length_cm are accepted, or send height_m in meters if that is how your form stores stature. Send age in years as a finite number in the closed interval from two to twenty; aliases age_years, years, and age_y are accepted. Send sex as male or female so the correct LMS series is selected; short aliases such as m and f, boy and girl, and numeric codes one and two are accepted. If age is below two or above twenty the request fails with invalid_input and is not charged, because these charts do not cover infants under two or adults past twenty. Identical inputs always yield identical JSON because the algorithm never touches the network, a model, a clock, or a random generator.

Reading BMI, percentile, bands, and common pitfalls

On success the response echoes weight_kg, height_cm, height_m, age_years, and sex, then reports bmi in kilograms per meter squared, bmi_z_score, and bmi_percentile on a zero-to-one-hundred scale. The band field is one of underweight, healthy_weight, overweight, or obesity, following CDC percentile cutoffs: below the fifth percentile, from the fifth up to but not including the eighty-fifth, from the eighty-fifth up to but not including the ninety-fifth, and at or above the ninety-fifth. The band_label field restates that rule in plain language for UI copy. Method is always cdc_bmi_for_age_lms and reference names the CDC two thousand charts so downstream code can branch without sniffing shapes.

API usage, pricing, school and clinic workflows, and practical limits

Call the free in-browser child and teen BMI calculator for quick checks, classroom demos, and caregiver education without installing a growth-chart spreadsheet. Prefer metric inputs that match the published CDC LMS units; if your UI collects pounds and inches, convert before calling. Keep expectations clinical: this is an educational and screening estimate aligned with CDC chart math, not a certified medical device, and families should follow professional advice when a band or growth trajectory raises concern. For infants under two years or adults over twenty, use age-appropriate tools rather than forcing this child-and-teen contract. Send a JSON body with required weight, height, age, and sex (or their documented aliases). Use the prepaid API when a pediatric intake form, school nurse workstation, sports physical app, telehealth triage flow, or research pipeline needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with your own consent and privacy layer before storing measurements about minors, and keep raw inputs under the same retention rules as other KIT parse items. Authors shipping SDKs can map band and bmi_percentile into dashboards, PDF visit summaries, and CSV exports labeled percentile and weight status—the same categories growth charts teach in pediatrics courses.